Abstract.
The substantial interspecies differences in mammalian cardiac action potentials (APs) are attributed primarily to variations in K+ currents. In a comparative study on isolated ventricular myocytes from guinea-pigs, rabbits and rats, we investigated the influence of the species-based AP differences on the time course of the L-type Ca2+ current (I Ca,L). In addition, we tested whether also species-dependent properties of the I Ca,L contribute to its time course during the AP. In patch-clamp measurements, I Ca,L was characterised using conventional square pulses and digitised APs as command voltages. Special interest was directed to the analysis of the actual time courses of I Ca,L, and L-type channel activation and inactivation during APs. Although species-specific differences in AP shape strongly influence the amplitude and the time course of I Ca,L, divergence in L-type channel inactivation was found as well. In each species I Ca,L inactivation was related to Ca2+ influx via L-type channels. However, while L-type channels showed similar Ca2+ dependency in the rabbit and the rat, a 2-times higher Ca2+ influx was necessary to achieve a given degree of inactivation in the guinea-pig. Thus, inactivation of I Ca,L is delayed in the guinea-pig, thereby contributing to the prolonged AP plateau in this species. Comparing the actual time course of I Ca,L, and L-type channel activation and inactivation revealed that, in each species, fading of I Ca,L during final repolarisation was caused by deactivation (i.e. closure of the channel's d-gate) rather than inactivation.
Similar content being viewed by others
Author information
Authors and Affiliations
Additional information
Electronic Publication
Rights and permissions
About this article
Cite this article
Linz, K., Meyer, R. Profile and kinetics of L-type calcium current during the cardiac ventricular action potential compared in guinea-pigs, rats and rabbits. Pflügers Arch – Eur J Physiol 439, 588–599 (2000). https://doi.org/10.1007/s004249900212
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/s004249900212